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Dengue and Dengue Hemorrhagic Fever:
Information for Health Care Practitioners
(en
español) Introduction
Dengue is an arthropod-borne disease caused by any one of four closely
related viruses. Infection with one serotype of dengue virus provides
immunity to that serotype for life. A person can be infected as
many as four times, once with each serotype. Dengue viruses are transmitted
from person to person by Aedes mosquitoes (most often Aedes
aegypti) in the domestic environment. Periodic epidemics have
occurred in the Western Hemisphere for over 200 years. In the past 20
years, dengue transmission and the frequency of dengue epidemics has
increased greatly in most tropical countries of the American region.
Clinical Diagnosis
Dengue
Classic dengue fever or "break bone fever" is characterized
by acute onset of high fever, 3-14 days after the bite of an infected
mosquito. Patients develop frontal headache, retro-orbital pain, myalgias,
arthralgias, nausea, vomiting, and often a maculopapular rash. Many patients
notice a change in taste sensation. Acute
symptoms,
when present, usually last about 1 week, but weakness, malaise, and anorexia
may persist for several weeks. A high proportion of infections produce
no or minimal symptoms, especially in children. Treatment emphasizes relief
of symptoms, avoiding aspirin and other non steroidal anti-inflamatory
medications and encouraging oral fluid intake (see Treatment below).
Dengue Hemorrhagic Fever/Dengue Shock Syndrome
Some patients with dengue fever go on to develop dengue hemorrhagic fever
(DHF), a severe and sometimes fatal form of the disease. At about the
time the fever begins to subside, the patient may become restless or lethargic,
show signs of circulatory failure, and experience hemorrhagic
manifestations. The most common of these manifestations are mild, such
as skin hemorrhages as petechiae or microscopic hematuria, but may also
include epistaxis, bleeding gums, hematemesis, and melena. DHF patients
develop thrombocytopenia and hemoconcentration, the latter as a result
of the leakage of plasma from the intravascular compartment. These patients
may rapidly progress into dengue shock syndrome (DSS), which, if not treated
correctly, can lead to profound shock and death. Despite the name, it
is the loss of intravascular volume from leaky capillaries rather than
hemorrhage, which results in shock. Advance warning signs of DSS include
severe abdominal pain, protracted vomiting, marked change in temperature
(from fever to hypothermia), or change in mental status (irritability
or obtundation). Early signs of shock include
restlessness, cold clammy skin, rapid weak pulse, narrowing of pulse pressure,
and hypotension. Fatality rates among those with DSS may be higher than
10%. DHF/DSS can occur in children and adults.
Treatment
Even for outpatients, the need for maintaining adequate hydration should
be stressed. In addition, monitoring for
signs of hemorrhagic fever and early appropriate treatment
are key to ensure survival if the patient progresses
to a more severe form of dengue infection. DHF/DSS can be effectively
managed by intravenous fluid replacement therapy, and if diagnosed
early, fatality rates can be kept below 1%. It is very important that
physicians and other health care providers learn to recognize this disease.
To manage the pain and fever, patients suspected of having a dengue infection
should be given acetaminophen preparations. Aspirin and non-steroidal
anti-inflammatory medications may aggravate the bleeding tendency associated
with some dengue infections and in children
can be associated with the development of Reyes syndrome.
Laboratory Diagnosis
Unequivocal diagnosis of dengue infection requires laboratory confirmation,
either by isolating the virus or detecting specific antibodies. For virus
isolation, an acute-phase serum specimen should be collected within 5
days after onset of fever. If virus cannot be isolated, a convalescent-phase
serum specimen is needed at least 6 days after onset of symptoms to make
a serologic diagnosis by enzyme-linked immunosorbent assay (ELISA). Acute-phase
and convalescent-phase serum samples should be collected and sent to the
state health department for testing or forwarded to CDC for testing. Acute-phase
samples for virus diagnosis may be stored on dry ice (-70°C)
or, if delivery can be made within 1 week, stored unfrozen in a refrigerator
(4°C). Convalescent-phase samples should be sent in a rigid container
without ice, if next-day delivery is assured. Otherwise they should be
shipped on ice, in an insulated container to avoid heat exposure during
transit.
It is important to note that most tests for anti-dengue antibodies are
non-specific among the flaviviruses, including West Nile and St. Louis
encephalitis viruses. Commercial kits may vary in sensitivity and specificity;
therefore critical results may need confirmation by a reference laboratory.
Epidemiology
A dengue epidemic requires the presence of 1) the vector mosquito (usually
Aedes aegypti), 2) the virus, and 3) a large number of susceptible
human hosts. Outbreaks may be explosive or progressive, depending on the
density and efficiency by which the vector can be
infected, the serotype and strain of dengue virus, the number of susceptible
humans in the population, and the amount of vector-human contact. Dengue
should be considered as the possible etiology where influenza,
rubella, or measles is suspected in a dengue-receptive area, i.e., at
a time and place where vector mosquito populations are abundant and active.
In most countries of the Caribbean Basin, Aedes aegypti is abundant
year-round. In the United States, this species is seasonally
abundant in some southwestern and southeastern states, including Texas
(Brazoria, Brazos, Collin, Dallas, Denton, El Paso, Ellis, Fort Bend,
Galveston, Hidalgo, Jefferson, McLennan, Midland, Montgomery, Nueces,
Orange, San Patricio, Tarrant, Taylor, and Travis counties), Arizona (Maricopa,
Pinal, Yavapai counties and Tucson,
Nogales, Douglas), New Mexico (Las Cruces), Louisiana (New Orleans, Monroe,
Lafayette), Mississippi, Alabama, Georgia, and mid to south Florida. It
has been sporadically reported from limited areas of North Carolina (Swain,
Haywood counties), South Carolina, Tennessee (Blount, Sevier counties),
Arkansas (Jefferson county), Maryland, and New Jersey (Morris county).
Given the competent vectors and susceptible population in the continental
United States isolated dengue outbreaks may occur (last
reported dengue in Texas in 1999).
In 1985, a mosquito from Asia, Aedes albopictus, was found in
the U.S. This species is now found in most states in the eastern half
of the U.S. and limited areas of Bolivia, Brazil, Cayman Islands, Colombia,
Cuba, Dominican Republic, El Salvador, Guatemala, Honduras, and Mexico.
Although
its contact with humans and its density in urban areas are not as great
as that of Aedes aegypti, this species can also transmit dengue
viruses. From
mid 2001 through early 2002, 122 Hawaii residents developed dengue infections
due to autochthonous transmission by Aedes albopictus mosquitoes.
As noted previously, the frequency of epidemic disease has increased significantly
in the past 20 years. Modern transportation makes it easy for travelers
to visit virtually any location on the globe, including areas of the world
where dengue is endemic.
Although
travel-associated dengue and limited outbreaks do occur in the continental
United States, most dengue cases in US citizens occur as a result of endemic
transmission in some of the US territories. CDC conducts laboratory-based
passive surveillance in Puerto Rico in collaboration with the Puerto Rico
Department of Health. The weekly surveillance report produced by this
collaboration can be found at:
Dengue Surveillance
Report for Puerto Rico.
If
a dengue-like illness is observed in a person in the continental United
States who has recently traveled to a tropical area, a blood specimen,
associated clinical information (case
form), and a brief travel history
should be sent to the state public health laboratory with a request that
the specimen be tested for dengue there or at the CDC's Dengue Branch
in San Juan, Puerto Rico. If that is not possible, contact the Centers
for Disease Control and Prevention at the address below.
In Puerto Rico and the U.S. Virgin Islands, specimens and clinical information
can be sent through the respective Department of Health or directly to
the address listed below (criteria
for specimen testing at CDC).
For further Information, contact:
Dengue Branch
Centers for Disease Control and Prevention
1324 Cañada Street
San Juan, Puerto Rico 00920-3860
Tel. (787) 706-2399; Fax (787) 706-2496
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